JPH073836Y2 - Ultrasonic motor drive circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a drive circuit for an ultrasonic motor, and more particularly to a drive circuit when a plurality of ultrasonic motors are used.

[Prior Art] As is well known, an ultrasonic motor configured to obtain a rotational motion or a linear motion by exciting ultrasonic vibration using an electrostrictive element, a piezoelectric element, or the like has been widely used in recent years. Compared to conventional electromagnetic motors, this ultrasonic motor is (1) easier to make smaller and thinner. (2) Low speed and high torque drive is possible. (3) The structure is simple. Therefore, it is suitable for use as a drive source for, for example, a camera autofocus device.

FIGS. 6, 7 and 8 are diagrams showing the driving principle of the ultrasonic motor, in which the plurality of piezoelectric elements 1 fixed to the elastic body 2 are
The piezoelectric elements 1 adjacent to each other are arranged so that their polarization directions are opposite to each other. Further, the plurality of piezoelectric elements 1 are divided into two groups, and the respective piezoelectric element groups 1A and 1B are mutually l / l when the length of a pair of adjacent piezoelectric elements 1 whose polarization directions are opposite to each other is l. It is fixed to the elastic body 2 at intervals of 4. Then, the elastic body 2 is attached to each of the piezoelectric element groups 1A and 1B.
When an AC voltage V having a resonance frequency ω determined by the material and shape of the vibrator 3 including the piezoelectric element 1 is applied with a phase shift of π / 2, an elastic traveling wave is excited on the surface of the elastic body 2. Each mass point on the surface of the elastic body 2 in which the traveling wave is excited performs elliptical vibration in the direction d opposite to the traveling direction c of the traveling wave. Therefore, as shown in FIG. 6, if a moving body 4 that makes frictional contact with the elastic body 2 is placed near the top of the crest of the traveling wave, this moving body 4 will move in the direction indicated by the arrow e along the direction d of the elliptical vibration. Move to. Reference numeral 5 is a slider provided on the moving body 4. The elastic body 2 may be arranged in an annular shape as shown in FIG. 6 or may be linearly arranged as shown in FIG. The structure for generating elliptical vibration due to a traveling wave can also be realized by arranging various piezoelectric elements as disclosed in Japanese Patent Laid-Open No. 59-96881. Furthermore, as disclosed in Japanese Patent Laid-Open No. 60-187271, it is possible to excite an elliptical vibration also by a standing wave vibration.

FIG. 9 shows a typical configuration of a drive circuit for driving the ultrasonic motor. The oscillator 6 generates an AC voltage having a resonance frequency of the ultrasonic motor 12. This voltage is directly input to one of the power amplifiers 8 and is phase-shifted by the 90 ° phase shifter 7 before being input to the other power amplifier 9. The outputs of both power amplifiers 8 and 9 are boosted by boosting transformers 10 and 11, respectively, and applied to the piezoelectric element groups 12A and 12B of the ultrasonic motor 12. The reason why the step-up transformers 10 and 11 are required is that if a battery is used as the power supply 13, the battery voltage cannot obtain an AC voltage of 100 V or more necessary for driving the ultrasonic motor.

[Problems to be Solved by the Invention] As described above, the ultrasonic motor has features that it can be easily miniaturized and thinned and can be driven at a low torque and a high torque. The problem is that it is more complicated than the conventional electromagnetic motor. In particular, when using a plurality of ultrasonic motors, how to reduce the load on the drive circuit has become an issue.

That is, in actually controlling the ultrasonic motor, it is difficult to make a plurality of motors having exactly the same resonance frequency. Therefore, the output of the power source that can output only an AC voltage of a single frequency is simply switched. It is difficult to control the drive of a plurality of motors by itself, and the ultrasonic motor has a resonance frequency in addition to the resonance frequency at which it can be efficiently driven. A motor other than the motor may be driven at a resonance frequency other than the resonance frequency at which the motor efficiently operates. Therefore, in order to switch the driving of a plurality of motors, it is desirable to simultaneously switch the frequency and the output of the drive circuit.

An object of the present invention is to provide a driving circuit for an ultrasonic motor that solves the above problems.

[Means and Actions for Solving Problems] In order to solve the above problems, the present invention provides an electric circuit for driving a plurality of ultrasonic motors,
While selecting the resonance frequency of the ultrasonic motor to drive,
The drive output is switched so that the drive circuit is connected only to the motor, thereby reducing the load on the circuit.

[Embodiment] The present invention will be described below with reference to the illustrated embodiment.

FIG. 1 is an electric circuit diagram of an ultrasonic motor drive circuit according to an embodiment of the present invention. This circuit is designed so that the CPU 21 controls the drive circuit. Memory 22 is CPU2
In addition to the program executed by 1, the most efficient resonance frequency of each of a plurality of selected and driven ultrasonic motors, for example, eight ultrasonic motors 25-1 to 25-8 in this embodiment. f is stored. The CPU 21 sends a signal to the oscillator 26 through the decoder 23 and also sends a signal to the switching circuit 30 through the other decoder 24.

The oscillator 26 is composed of a variable frequency oscillator, as shown in FIG. That is, the oscillation circuit, resistors R _{1 to} R ₈ , R _φ for changing the oscillation frequency and capacitors C ₁ and C _φ , FET switches Q _{1 to} Q ₈ for switching the resistors R _{1 to} R ₈ , and The operational amplifier OP, resistors R _{a to} R _h and R _φ0 that change the gain so that the oscillator does not stop when the oscillation frequency is changed, and the resistors R _{a to} R _h.
It is formed by connecting, as shown and FET switch Q _a to Q _h for switching. The oscillation frequency f in the oscillation circuit formed in this way is Is determined by. Further, the above FET switches Q _{1 to} Q ₈ and Q _a
To Q _h is the signal applied respectively from the decoder 23 to the control terminal I ₁ ~I ₈ if the H (high) input signal, an on state when off the L (low) input signal.

Output OUT of variable frequency oscillator 26 configured in this way
1 is input to the switching circuit 30 through one power amplifier 28, and is also input to the switching circuit 30 through the 90 ° phase shifter 27 and the other power amplifier 29, as shown in FIG.

The switching circuit 30 has step-up transformers 31 and 32 (see FIG. 3) for stepping up the outputs of the power amplifiers 28 and 29, respectively.
It serves to switch the output circuit so that only the desired ultrasonic motor operates from among -1 to 25-8. The switching circuit 30 is constructed as shown in FIG. In the switching circuit 30 of FIG. 3, switching is performed by using well-known solid state relays 33A to 33D. It should be noted that in the example of FIG. 3, two ultrasonic motors will be described for convenience of explanation.

That is, the solid state relays 33A and 33B are connected between the output terminals of the step-up transformers 31 and 32 and the ultrasonic motor 25-1, and are connected to the input terminal 36a of the input circuit including the transistor 34a and the resistor 35a. The ON / OFF operation is controlled by the applied input signal from the decoder 24 (see FIG. 1). The solid state relays 33C and 33D output the boost transformers 31 and 32. It is connected between the end and the ultrasonic motor 25-2. The on / off operation is controlled by an input signal applied through the decoder 24 to the input terminal 36b of the input circuit including the transistor 34b and the resistor 35b. In the switching circuit 30, when the motor 25-1 is driven,
An H level signal is applied to the input terminal 36a. Then, the transistor 34a turns on, and the solid state relays 33A, 3A
The diode LED in 3B emits light, and the thyristor SCR incorporated so as to conduct in the phase direction is turned on, and the step-up transformer 3
The outputs of 1,32 are supplied to the motor 25-1, which operates. Further, when the other motor 25-2 is driven, an H level signal is similarly applied to the input terminal 36b.

In this example, a solid-state relay is used as the switching element, but this may be configured by using an SCR, bipolar Tr, power MOS, or other ordinary electromagnetic relay if control time is allowed. Good.

The operation of the drive circuit shown in FIG. 1 constructed as above will be described. The CPU 21 first reads the resonance frequency data of the motor to be driven from the memory 22, and then the decoder 23.
Signal to control terminals I _{1 to} I ₈ via
The oscillation frequency f of 26 (see FIG. 2) is set to the target frequency. Then, the output at this oscillation frequency is power-amplified by the power amplifiers 28 and 29, then input to the switching circuit 30, and boosted by the boosting transformers 31 and 32. Also the above CPU
21 sets the decoder 22 at the same time as setting the decoder 22, so that the AC drive voltage is applied only to the target motor having the above-mentioned resonance frequency (see FIG. 3). ) To the switching circuit 30
Conduct the solid state relays 33A to 33D of. Then, the driving AC voltage boosted by the step-up transformers 31 and 32 is supplied to the target motor through the conductive relay, so that only the selected ultrasonic motor can be driven.

FIG. 4 shows another example of the switching circuit 30 shown in FIG. In the switching circuit 30 shown in FIG. 3, the secondary sides of the step-up transformers 31 and 32 are switched to control the driving of the motor. However, the switching circuit 30A shown in FIG.
Is a circuit in which the primary side of the step-up transformers 31A, 32A and 31B, 32B is switched to control the motor drive, and the switching circuit is composed of a bipolar Tr (transistor).

In the example shown in FIG. 4, two ultrasonic motors are used for convenience of explanation.

That is, in this example, four sets of switch circuits 40A, 40B, 40C, 40D shown in the block of the dotted line are used.
0A is between the power amplifier 28 and the primary side of the step-up transformer 31B,
The switch circuit 40B is one of the power amplifier 29 and the step-up transformer 32B.
The switch circuit 40C is connected between the power amplifier 28 and the primary side of the step-up transformer 31A, and the switch circuit 40D is connected between the power amplifier 29 and the primary side of the step-up transformer 32A. The ultrasonic motor 25-1 is supplied with drive voltage from the secondary side of the step-up transformers 31A and 32A, and the motor 25-2 is supplied with drive voltage from the secondary side of the step-up transformers 31B and 32B.

The configurations of the switch circuits 40A to 40D are exactly the same, and one of them is the switch circuit 40A, the transistors 41a, 42a and 43 connected in push-pull.
a, 44a, resistors 46a to 49a, and a transistor 45a are connected as shown in the figure. Switch circuit 40C, 40D
The circuit configuration inside is the same as that inside the circuit 40A, and is therefore omitted. And the switch circuits 40A and 40B are
An ON / OFF operation is controlled by an input circuit which is composed of a transistor 37a and a resistor 38a, and an input signal from the decoder 24 (see FIG. 1) is applied to an input terminal 39a, and the switch circuits 40C and 40D are connected to the transistor 37b. The ON / OFF operation is controlled by an input circuit formed by the resistor 38b and having the input signal from the decoder 24 applied to the input terminal 39b.

In the switching circuit 30A of FIG. 4 configured as above, the input terminal 39a is set to the H level when driving the motor 25-2. Then, the transistor 41a assembled in push-pull,
Since 42a and transistors 41b and 42b are turned on, the power amplifier
The outputs of 28 and 29 are applied to the primary side of the step-up transformers 31B and 32B, and the voltage boosted by the respective transformers 31B and 32B is applied to the motor 25-.
2 and the same motor 25-2 is driven. When the motor is stopped, the input terminal 39a is set to L level. Then, the transistor 37a is turned on, and the collector current of the transistor 37a causes the transistors 43a, 44a, 4a.
5a and transistors 43b, 44b, 45b are turned on. Thus, the base potentials of the push-pull transistors 41a, 42a and 41b, 42b that have been supplying power to the step-up transformers 31B, 32B become the same as the ground GND, so that the transistors are turned off. Therefore, the motor 25-2 stops rapidly.
Similarly, the drive of the motor 25-1 can be controlled by applying H-level and L-level signals to the input terminal 39b.

Instead of the bipolar transistor, SCR, power MOS, electromagnetic relay, etc. may be used.

FIG. 5 is an electric circuit of a drive circuit showing another embodiment of the present invention. The ultrasonic motors 25A and 25B driven by this circuit are
It is assumed that each resonance frequency is different due to the difference in material shape. For convenience of explanation, this embodiment will be described with two ultrasonic motors.

In this embodiment, oscillators 50A, 50 having different oscillation frequencies are used.
The output of B is switched by switching circuits 60A and 60B, respectively, and supplied to power amplifiers 8 and 9. Above oscillator 5
0A is an operational amplifier 51a, capacitors 52a and 53a, and a resistor 54a.
~ 57a are connected as shown in the figure, and the output of the resonance frequency required for the ultrasonic motor 25A is applied to the switching circuit 60A, and the oscillator 50B includes an operational amplifier 51b, capacitors 52b, 53b and resistors 54b-57b. Are connected as described above, and each is configured to apply the output of the resonance frequency required for the ultrasonic motor 25B to the switching circuit 60B.

The switching circuits 60A and 60B are constructed in exactly the same way as the switching circuits 40A to 40D shown in FIG. That is,
One switching circuit 60A is configured by connecting transistors 61a, 62a and 63a, 64a connected to push-pull, resistors 66a to 69a and a transistor 65a as shown in the figure, and an input circuit including a transistor 70a and a resistor 71a. The ON / OFF control is performed by a signal applied to the input terminal 72a of the switch 72A, and the output end of the switching circuit 60A is connected to the power amplifier 8 and the 90 ° phaser 7. The other switching circuit 60B is also composed of the transistors 61b, 62b and 63b, 64b, the resistors 66b to 69b and the transistor 65b, similarly to the one switching circuit 60A, and is connected to the input terminal 72b of the input circuit of the transistor 70b and the resistor 71b. The ON / OFF control is performed by the applied signal.
The output terminal of B is also connected to the power amplifier 8 and the 90 ° phase shifter 7. The power amplifiers 8 and 9, the 90 ° phase shifter, the step-up transformers 10 and 11, the battery power source 13 and the like are configured similarly to the conventional ones.

In the embodiment of FIG. 5 configured in this way,
When driving one ultrasonic motor 25A, the input terminal 72a is set to H level. Then, the output of the oscillator 50A turned on, a transistor in a push-pull configuration.
It is input to the power amplifiers 8 and 9 through 61a and 62a. Therefore, only the necessary AC voltage is applied to the motor 25A, and the motor 25A is efficiently driven. To stop the motor 25A, the input terminal 72a may be set to L level. Then, the transistor 70a turns on, and the collector current of the transistor 70a turns on the transistors 63a, 64a, and 65a. Transistors 61a, 62a connected in push-pull by this
The base potential of becomes the ground GND, and the same transistor 6
1a and 62a turn off. Therefore, the output of the oscillator 50A is not input to the power amplifiers 8 and 9, so that the motor 25A stops rapidly.

The driving of the other ultrasonic motor 25B is similarly controlled by the H level and L level signals applied to the input terminal 72b.

In the present embodiment, the switching circuits 60A and 60B are formed by switching circuits using bipolar transistors.
The SCR, power MOS, solid-state relay, or an ordinary electromagnetic relay may be used if the control time permits.

[Effect of the Invention] As described above, according to the present invention, when driving a plurality of ultrasonic motors, the resonance frequency of the motors to be driven is selected and the output of the drive circuit is supplied only to the motors. By doing so, the number of common components of the drive circuit increases, and the load during circuit fabrication can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram of an ultrasonic motor drive circuit showing an embodiment of the present invention, FIG. 2 is a concrete electric circuit diagram of the oscillator in FIG. 1, and FIG. 1 is an electric circuit diagram showing an example of the switching circuit in FIG. 1, FIG. 4 is an electric circuit diagram showing another example of the switching circuit in FIG. 1, and FIG. 5 is another embodiment of the present invention. The electric circuit diagram of the drive circuit of the ultrasonic motor shown in FIGS. 6 to 8 is a diagram for explaining the drive principle of the ultrasonic motor, and FIG. 9 shows the basic configuration of the drive circuit of the ultrasonic motor. It is an electric circuit diagram shown. 1 ... Piezoelectric element 2 ... Elastic body 4 ... Moving body 6,26,50A, 50B ... Oscillator 12,25-1 to 25-8,25A, 25B ... Ultrasonic motor

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Toshiyuki Toyofuku Toshiyuki Toyofuku 2-43-2, Hatagaya, Shibuya-ku, Tokyo Inside Olympus Optical Co., Ltd. (72) Inventor Ryuji Imai 2-43-2, Hatagaya, Shibuya-ku, Tokyo No. Olympus Optical Co., Ltd. (56) Reference JP-A-63-205591 (JP, A) JP-A-57-81631 (JP, A) Practical application Sho-63-131596 (JP, U)

Claims (1)

[Scope of utility model registration request] 1. An ultrasonic motor for driving a moving body in which an elliptical vibration is generated on a surface of the elastic body by applying an AC voltage to a piezoelectric element fixed to the elastic body and the frictional contact is made on the surface. An ultrasonic motor drive circuit for driving a plurality of oscillators, the oscillator being capable of oscillating by switching a drive frequency signal suitable for each of the plurality of ultrasonic motors, and an output signal of the oscillator being received on a primary side, A transformer that amplifies the output signal and outputs it to the secondary side as the AC voltage, and a plurality of solid state provided between the secondary side of the transformer and each of the piezoelectric elements in the plurality of ultrasonic motors. Selecting means for selectively applying the AC voltage output from the transformer to one of the plurality of ultrasonic motors, the relay comprising: To select one, to control the oscillator to oscillate a drive frequency signal suitable for the selected ultrasonic motor, and to connect between the selected ultrasonic motor and the transformer, A drive circuit for an ultrasonic motor, comprising: a control unit that controls the selection unit.